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7
7.4
Transmission types
transmission type
PDO transmission
cyclic
acyclic
synchronou
s
asynchronou
s
RTR only
0
X
X
1-240
X
X
241-251
- Reserved -
252
X
X
253
X
X
254
X
255
X
Table 7-3. Description of transmission type
Synchronous (transmission types 0-240 and 252) means that the transmission of the PDO shall be
related to the SYNC object. Preferably the devices use the SYNC as a trigger to output or actuate
based on the previous synchronous Receive PDO respectively to update the data transmitted at the
following synchronous Transmit PDO. Asynchronous means that the transmission of the PDO is not
related to the SYNC object. A transmission type of zero means that the message shall be transmitted
synchronously with the SYNC object but not periodically. A value between 1 and 240 means that the
PDO is transferred synchronously and cyclically. The transmission type indicating the number of
SYNC which are necessary to trigger PDO transmissions. Receive PDOs are always triggered by the
following SYNC upon reception of data independent of the transmission types 0 - 240.
The transmission types 252 and 253 mean that the PDO is only transmitted on remote transmission
request. At transmission type 252, the data is updated (but not sent) immediately after reception of
the SYNC object. At transmission type 253 the data is updated at the reception of the remote
transmission request (hardware and software restrictions may apply). These value are only possible
for TPDOs. For TPDOs transmission type 254 means, the application event is manufacturer specific
(manufacturer specific part of the Object Dictionary), transmission type 255 means, that the
application event is defined in the device profile. RPDOs with that type trigger the update of the
mapped data with the reception. PDOs Sub-index 3h contains the inhibit time. This time is a minimum
interval for PDO transmission. The value is defined as multiple of 100
μ
s. It is not allowed to change
the value while the PDO exists (Bit 31 of sub-index 1 is 0).
In mode 254/255 additionally an event time can be used for TPDO. If an event timer exists for a TPDO
(value not equal to 0) the elapsed timer is considered to be an event. The event timer elapses as
multiple of 1 ms of the entry in sub-index 5h of the TPDO. This event will cause the transmission of
this TPDO in addition to otherwise defined events. The occurence of the events set the timer.
Independent of the transmission type the RPDO event timer is used recognize the expiration of the
RPDO.
